This invention relates to sleeping bags.
Single and double sleeping bags are well known, but most of the types available are suitable--as their name indicates--for sleeping only one person, or only two persons. That is to say, two persons cannot squeeze into a single bag and a double bag is not suitable for sleeping one person only, especially in cold environments. In the past, these problems have been approached by constructing double sleeping bags of two separate panels which are zip-fastened together along three adjacent edges. Each panel, when separated, can be folded along a centre-line to form a single bag, with the bottom and the free side edges being zip-fastened, and the side of the bag opposite the zip-fastened side being formed along the line of folding. The top edges, of course, are not joined together and this provides an entrace to the bag at the head thereof. A further approach to the above problems has been disclosed in U.S. Pat. No. 3,965,505 to S. W. Thorowgood.
The Thorowgood Patent discloses a double sleeping bag having a pair of panels which are fastened together along the bottom and the side edges leaving the edges at the head or "top" of the bag unfastened to provide an entrance thereto. The bag is so constructed and arranged that it can be folded along its centreline whereby one of the panels forms the outside and the other panel forms the inside of a double sleeping bag.
In effect, this is a similar arrangement to that previously tried except that two panels rather than one panel are folded to form a single sleeping bag. All of these prior arrangements involve problems when hooded bags are used. For example, the bottom panel of a hooded double sleeping bag cannot be folded to form a single sleeping bag as the resulting bag would have a hood affixed below and above a sleeper's head. Similarly, two hooded single sleeping bags cannot be satisfactorily joined together to make a hooded sleeping bag of double size as the resulting bag would have a hood on its bottom panel and a hood on its top panel instead of two hoods side by side on the bottom panel. This applies where each single bag is opened out into a double size panel first, before being joined to the other, but not where the two single bags are joined together without being opened out. This latter arrangement has its own disadvantages as described in the Thorowgood Patent at Column 1, paragraph 1. Viz--the sleeping bags must in general be of similar design and the method of joining results in the zip fastener being positioned in the module of the resulting bag.